This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2000-382221 filed on Dec. 15, 2000 and No. 2001-371746 filed on Dec. 5, 2001, the entire contents of which are incorporated by reference herein.
1. Field of the Invention
The present invention relates to etching for manufacture of semiconductor devices, more particularly, to etching for an insulating film such as an oxide film, a nitride film, or the like, and residual reaction products or the like after dry etching.
2. Description of the Related Art
In the manufacturing process of a semiconductor device, various films different from one another in a property are formed on a semiconductor substrate. Thus, for an etching process, an etching condition must be set according to a property of each film.
In addition, a plurality of films are normally laminated on the semiconductor substrate. In many cases, a plurality of films different from one another in a property are exposed to the surface of the substrate at the time of starting etching or during the etching process. In the etching process, there may be a case where only a specified one among the plurality of exposed films needs to be selectively etched, or a case where the plurality of films different from one another in a property need to be unselectively etched simultaneously.
For example, insulating films to be formed on the semiconductor substrate include a thermal oxide SiO2 film obtained by thermal oxidation, a TEOS (tetra ethoxy silane) film obtained by a thermal CVD method, a TEOS film obtained by a plasma CVD method, a BPSG(boron phosphor silicate glass) film, a PSG(phosphor silicate glass) film and a BSG (boron silicate glass) film obtained by a CVD method, a SiN(silicon nitride) film and a SiON(silicon oxide nitride) film obtained by various CVD methods, and the like. Among these, a plurality of insulating films may be exposed to the surface of the semiconductor substrate. In a case, selective etching must be performed for only one of such insulating films. In another case, unselective etching must be performed for a plurality of insulating films.
Conventionally, chemical components have been selected to prepare an etching solution for each process depending on a property of a film to be etched or a required etching condition. Thus, various kinds of an etching solution have been used as such an etching solution, and etching apparatuses have respectively been used for individual cases.
For example, conventionally, in the case of etching for an oxide film, buffered hydrofluoric acid obtained by mixing a hydrofluoric acid (HF) solution with an ammonium fluoride solution, or an etching solution obtained by mixing a phosphoric acid solution with a hydrofluoric acid solution has been used. In addition, Japanese Patent Laid-Open publication P2000-164586 discloses the use of an etching solution obtained by mixing a hydrofluoric acid solution with inorganic acid such as acetic acid or the like, or a solution obtained by mixing a hydrofluoric acid solution with organic acid such as ethanol or the like, regarding selective etching carried out for a BSG film or a BPSG film with respect to a thermal oxide SiO2 film.
An etching solution that has widely been used in a conventional case includes one containing phosphoric acid (H3PO4) in addition to the hydrofluoric acid solution, and the ammonium fluoride solution. For example, as a method of highly selectively etching SiN with respect to SiO2, high-temperature etching of 160xc2x0 C. using a mixed solution of phosphoric acid and water has been known. However, this method needs a dedicated apparatus for using H3PO4, and there is a high possibility of scattering of phosphorus (P) into a clean room atmosphere. Thus, an alternative process has been desired.
Furthermore, it has been reported that when a mixed solution of an organic material and acid is used as an etching solution for selective etching of a BSG film or a BPSG film with respect to a thermal oxide SiO2 film, an etching temperature can be more lowered. However, the disposal of a waste solution of the organic material and the acid necessitates time and labor.
As described above, conventionally, chemical components have been selected to prepare an etching solution for each etching process depending on a property of a film to be etched or a required etching condition. Consequently, an etching apparatus has been necessary for each purpose, causing great burdens in terms of costs of chemical solutions and apparatuses, an occupied space in a manufacturing line, and chemical disposal after etching.
According to a first aspect of the present invention, a method of manufacture of semiconductor devices includes etching carried out by using a solution containing H2SO4 and NH4F, alternatively H2SO4 and HF, as main components, and having an H2O content set to 5 wt % or lower as an undiluted etching solution.
According to a second aspect of the invention, a method of manufacture of semiconductor devices includes selective etching carried out for an SiN film with respect to one selected from an SiO2 film, an Si substrate, and an Si film at an azeotropic point temperature, by using a mixed solution of H2SO4 and H2O having an azeotropic point set at 150xc2x0 C. or higher as an etching solution.
According to a third aspect of the invention, a method of manufacture of semiconductor devices includes selective etching for an SiN film or an SiON film formed by a CVD method with respect to one selected from an SiO2 film, an Si substrate, and an Si film at an etching solution temperature of 150xc2x0 C. or higher, by using a mixed solution of H2SO4 and H2O having an H2O content set at 10 wt % to 40 wt % with respect to the H2SO4 as an etching solution.
According to a fourth aspect of the invention, a method of manufacture of semiconductor devices includes selective etching carried out for an SiN film or an SiON film formed by a CVD method with respect to one selected from an SiO2 film, an Si substrate, and an Si film at an azeotropic point temperature, by using a solution obtained by adding HF of 0.1 wt % or lower to a mixed solution of H2SO4 and H2O having an azeotropic point set at 100xc2x0 C. or higher as an etching solution.
According to a fifth aspect of the invention, a method of manufacture of semiconductor devices includes selective etching carried out for an SiN film or an SiON film formed by a CVD method with respect to one selected from an SiO2 film, an Si substrate, and an Si film at an etching solution temperature of 120xc2x0 C. or higher, by using a solution obtained by adding HF of 0.1 wt % or lower to a mixed solution of H2SO4 and H2O having an H2O content set at 10 wt % to 50 wt % with respect to the H2SO4.
According to a sixth aspect of the invention, a method of manufacture of semiconductor devices includes selectively etching a specific one or a plurality of insulating films among a plurality of films different from one another in a property, and exposed to a surface of a semiconductor substrate, with respect to another film, by using a first etching solution. The first etching solution is an undiluted etching solution containing H2SO4 and NH4F, or H2SO4 and HF as main components, and having an H2O content set to 5 wt % or lower, alternatively a solution obtained by diluting the undiluted etching solution by a sulfuric acid solution having an H2O content set at 5 wt % or lower. The method also includes another selectively etching a specific one or a plurality of insulating films among a plurality of films different from one another in a property, and exposed to the surface of the semiconductor substrate by using a second etching solution. The second etching solution is the undiluted etching solution, alternatively a solution obtained by diluting the undiluted etching solution by the sulfuric acid solution having the H2O content set at 5 wt % or lower. Furthermore the method includes unselective etching a plurality of insulating films exposed to the surface of the semiconductor substrate by using a third etching solution. The third etching solution is the undiluted etching solution, alternatively a solution obtained by diluting the undiluted etching solution by the sulfuric acid solution having the H2O content set at 5 wt % or lower.
According to a seventh aspect of the invention, a method of manufacture of semiconductor devices includes etching an insulating film exposed to a surface of a semiconductor substrate by using an etching solution. The etching solution is an undiluted etching solution containing H2SO4 and NH4F, alternatively H2SO4 and HF as main components, and having an H2O content set to 5 wt % or lower, alternatively a solution obtained by diluting the undiluted etching solution by sulfuric acid solution having an H2O content set at 5 wt % or lower. The method also includes subjecting the surface of the semiconductor substrate after the etching step to preliminary cleaning by a sulfuric acid solution having an H2O content set at 5 wt % or lower. Furthermore the method includes subjecting the surface of the semiconductor substrate after the preliminary cleaning to real cleaning by pure water.